installation doc: cmake unclear and failing

[Peter Baumann]

In the doc at ​http://doc.rasdaman.org/02_inst-guide.html#download-and-install-rasdaman there is a line

cmake .. [ -D<option>... ]

To improve here:

• first provide the concrete command to execute, do NOT show some meta yntax where users expect to copy-paste.
• (optional) guidance comes only after explanation of all the options. According to the funnel GUI pattern, that explanation should be a sideline, but not be on the mainline.
• the command indicated does not work for me:

  cmake .. -DCMAKE_INSTALL_PREFIX=$RMANHOME -DCMAKE_BUILD_TYPE=Release \
             -DUSE_NETCDF=ON -DUSE_GRIB=ON -DFILE_DATA_DIR=$RMANHOME/data \
             -DWAR_DIR=/var/lib/tomcat/webapps
  

I get the error message:

~/build$ cmake .. -DCMAKE_INSTALL_PREFIX=$RMANHOME -DCMAKE_BUILD_TYPE=Release \
>            -DUSE_NETCDF=ON -DUSE_GRIB=ON -DFILE_DATA_DIR=$RMANHOME/data \
>            -DWAR_DIR=/var/lib/tomcat/webapps
CMake Error: The source directory "/home/rasdaman" does not appear to contain CMakeLists.txt.
Specify --help for usage, or press the help button on the CMake GUI.

…which makes sense as said file is in ../rasdaman . With this directory, cmake succeeds. However, for simplicity I recommend changing to

cd ../rasdaman
cmake ...